XLENGTH
if (ymax < YDEPTH + 2 || xmax < XLENGTH + 4) {
xbase = (xmax - XLENGTH) / 2 + 2;
hline(ACS_HLINE, XLENGTH);
mvaddch(ybase - 2, xbase - 2 + XLENGTH, ACS_URCORNER);
hline(ACS_HLINE, XLENGTH);
mvaddch(ybase + YDEPTH - 1, xbase - 2 + XLENGTH, ACS_LRCORNER);
move(ybase - 1, xbase - 2 + XLENGTH);